How about returning up front? Say for example, if monster.pl contains:
#!/usr/bin/perl
sub mysub {print "I want to see this\n"};
print "but I don't want to see this\n";
exit; # don't want to exit either
Then:
#!/usr/bin/perl
use warnings;
use strict;
my $prog_code = do {local $/ = undef;
open (my $fh, '<', 'monster.pl')
or die "open error: $!";
<$fh>};
eval 'return;'.$prog_code ;
die "eval error: $@" if $@;
warn "trying mysub";
mysub();
The return gets executed as soon as compilation has finished, avoiding execution of the main body:
perl do.pl
trying mysub at do.pl line 13.
I want to see this
Compilation finished at Wed Aug 4 10:08:26
Update: Removed intermediate subroutine and added sample output.