.TH GPERL 1 "19 March 2021" "groff 1.22.4"
.SH NAME
gperl \- groff preprocessor for Perl parts in roff files
.
.\" ====================================================================
.\" Legal Terms
.\" ====================================================================
.\"
.\" Copyright (C) 2014-2018 Free Software Foundation, Inc.
.\"
.\" This file is part of gperl, which is part of groff, a free software
.\" project.
.\"
.\" You can redistribute it and/or modify it under the terms of the GNU
.\" General Public License as published by the Free Software Foundation,
.\" version 2.
.\"
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.\" <http://www.gnu.org/licenses/gpl-2.0.html>.
.
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.\" Characters
.\" ====================================================================
.
.\" Ellipsis ...
.ie t .ds EL \fS\N'188'\fP\"
.el .ds EL \&.\|.\|.\&\"
.\" called with \*(EL
.
.\" Bullet
.ie t .ds BU \(bu
.el .ds BU *
.\" used in '.IP \*(BU 2m' (former .Topic)
.
.
.\" ====================================================================
.SH "SYNOPSIS"
.\" ====================================================================
.
.SY gperl
.RI [ filespec
\*(EL]
.YS
.
.SY gperl
.B \-h
.SY gperl
.B \-\-help
.YS
.
.SY gperl
.B \-v
.SY gperl
.B \-\-version
.YS
.
.
.\" ====================================================================
.SH DESCRIPTION
.\" ====================================================================
.
This is a preprocessor for
.BR \%groff (1).
.
It allows the use of
.BR perl (7)
code in
.BR groff (7)
files.
.
The result of a
.I Perl part
can be stored in groff
.I strings
or
.I numerical registers
based on the arguments at a final line of a
.IR "Perl part" .
.
.
.\" ====================================================================
.SH "OPTIONS"
.\" ====================================================================
.
So far, there are only
.I filespec
or
.I breaking
options.
.
.
.P
.I filespec
are file names or the minus character
.B \-
character for standard input.
.
As usual, the argument
.B \-\-
can be used in order to let all following arguments mean file names,
even if the names begin with a minus character
.BR \- .
.
.
.P
An option is
.IR breaking ,
when the program just writes the information that was asked for and
then stops.
.
All other arguments will be ignored by that.
.
These
.I breaking
options are here
.
.TP
.B \-h\~\fR|\fB\~\-\-help
Print help information with a short explanation of options to
standard output.
.
.
.TP
.B \-v\~\fR|\fB\~\-\-version
Print version information to standard output.
.
.
.\" ====================================================================
.SH "PERL PARTS"
.\" ====================================================================
.
.I Perl
parts in
.I groff files
are enclosed by two
.B .Perl
requests with different arguments, a
.I starting
and an
.I ending
command.
.
.
.\" ====================================================================
.SS "Starting Perl Mode"
.\" ====================================================================
.
The starting
.I Perl request
can either be without arguments, or by a request that has the term
.B start
as its only argument.
.RS
.IP \*(BU 2m
.B .Perl
.IP \*(BU 2m
.B .Perl start
.RE
.
.
.\" ====================================================================
.SS "Ending Perl Mode without Storage"
.\" ====================================================================
.
A
.B .Perl
command line with an argument different from
.B start
finishes a running
.IR "Perl part" .
.
Of course, it would be reasonable to add the argument
.BR stop ;
that's possible, but not necessary.
.
.RS
.IP \*(BU 2m
.B .Perl stop
.IP \*(BU 2m
.BI .Perl " other_than_start"
.RE
.
The argument
.I other_than_start
can additionally be used as a
.I groff
string variable name for storage \(em see next section.
.
.
.\" ====================================================================
.SS "Ending Perl Mode with Storage"
.\" ====================================================================
.
A useful feature of
.B gperl
is to store one or more results from the
.IR "Perl mode" .
.
.
.P
The output of a
.I Perl part
can be got with backticks
.BR \[ga]...\[ga] .
.
.
.P
This program collects all printing to STDOUT (normal standard output)
by the Perl
.B print
program.
.
This pseudo-printing output can have several lines, due to printed
line breaks with
.BR \(rsn .
.
By that, the output of a Perl run should be stored into a Perl array,
with a single line for each array member.
.
.
.P
This Perl array output can be stored by
.B gperl
in either
.TP
.I groff strings
by creating a groff command
.B .ds
.
.TP
.I groff number register
by creating a groff command
.B .rn
.
.
.P
The storage modes can be determined by arguments of a final stopping
.B .Perl
command.
.
Each argument
.B .ds
changes the mode into
.I groff string
and
.B .nr
changes the mode into
.I groff number register
for all following output parts.
.
.
.P
By default, all output is saved as strings, so
.B .ds
is not really needed before the first
.B .nr
command.
.
That suits to
.BR \%groff (7),
because every output can be saved as
.I groff
string, but the number registers can be very restrictive.
.
.
.P
In
.IR "string mode" ,
.B gperl
generates a
.I groff string
storage line
.RS
.EX
.BI .ds " var_name content"
.EE
.RE
.
In
.I number register mode
the following groff command is generated
.RS
.EX
.BI .nr " var_name content"
.EE
.RE
.
.
.P
We present argument collections in the following.
.
You can add as first argument for all
.BR stop .
.
We omit this additional element.
.
.
.P
.TP
.BI ".Perl .ds " var_name
This will store 1 output line into the groff string named
.I var_name
by the automatically created command
.RS
.RS
.EX
.BI .ds " var_name output"
.EE
.RE
.RE
.
.
.TP
.BI .Perl " var_name"
If
.I var_name
is different from
.B start
this is equivalent to the former command, because the string mode is
string with
.B .ds
command.
default.
.
.
.TP
.BI .Perl " var_name1 var_name2"
This will store 2 output lines into groff string names
.I var_name1
and
.IR var_name2 ,
because the default mode
.B .ds
is active, such that no
.B .ds
argument is needed.
.
Of course, this is equivalent to
.RS
.RS
.EX
.BI ".Perl .ds " "var_name1 var_name2"
.EE
.RE
and
.RS
.EX
.BI ".Perl .ds " "var_name1 " ".ds" " var_name2"
.EE
.RE
.RE
.
.
.TP
.BI ".Perl .nr" " var_name1 varname2"
stores both variables as number register variables.
.
.B gperl
generates
.RS
.EX
.BI .nr " var_name1 output_line1"
.BI .nr " var_name2 output_line2"
.EE
.RE
.
.
.TP
.BI ".Perl .nr " var_name1 " .ds " var_name2
stores the 1st argument as
.I number register
and the second as
.I string
by
.RS
.EX
.BI .nr " var_name1 output_line1"
.BI .ds " var_name2 output_line2"
.EE
.RE
.
.
.\" ====================================================================
.SS "Printing towards STDERR is without Storage"
.\" ====================================================================
.
The printing towards
.IR STDERR ,
(standard error) works as usual.
.
All error information goes to the real normal
.IR "standard error" ,
without other automatic storage.
.
.
.\" ====================================================================
.SH "EXAMPLES"
.\" ====================================================================
.
A possible
.I Perl part
in a
.I roff file
could look like that:
.RS
.EX
before
\&.Perl start
my $result = 'some data';
print $result;
\&.Perl stop .ds string_var
after
.EE
.RE
.
.
.P
This stores the result
.B \(rqsome data\(rq
into the
.I roff string
called
.BR string_var ,
such that the following line is printed:
.RS
.EX
\&.ds string_var some data
.EE
.RE
by
.B gperl
as food for the coming
.B groff
run.
.
.
.P
A
.I Perl part
with several outputs is:
.RS
.EX
\&.Perl start
print \(rqfirst\(rsn\(rq;
print \(rqsecond line\(rsn\(rq;
print \(rq3\(rsn\(rq;
\&.Perl var1 var2 .nr var3
.EE
.RE
.
This stores 3 printed lines into 3
.I groff
strings.
.BR var1 , var2 , var3 .
.
So the following
.I groff
command lines are created:
.RS
.EX
\&.ds var1 first
\&.ds var2 second line
\&.nr var3 3
.EE
.RE
.
.
.\" ====================================================================
.SH AUTHORS
.\" ====================================================================
.B gperl
was written by
.MT groff\-bernd.warken\-72@\:web.de
Bernd Warken
.ME .
.
.
.\" ====================================================================
.SH "SEE ALSO"
.\" ====================================================================
.
.P
Man pages related to
.I groff
are
.BR \%groff (1),
.BR \%groff (7),
.BR \%grog (1),
and
.BR \%groffer (1).
.
.
.P
Documents related to
.I Perl
are
.BR \%perl (1),
.BR \%perl (7).
.
.
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