On Tue, Mar 19, 2013 at 12:21:10AM -0300, Brian Fraser wrote: > You can just pipe a program into perl and it'll DWIM: > > $ echo 'print "Hello World, Perl $^V\n"' | perl
You can also be more explict about the program being on STDIN:
bash$ echo 'print "Hello , World!\n"' | perl -
The - tells it to read the program from STDIN. This allows you to
pass arguments to the program if necessary.
bash$ echo 'print "$_\n" for @ARGV' | perl - foo bar baz
From within Perl you can open a pipe to perl. For example:
#!/usr/bin/perl
use strict;
use warnings;
my $program = <<'EOF';
use strict;
use warnings;
print "$_\n" for @ARGV;
EOF
my @args = qw(foo bar baz);
open my $fh, '|-', qw(perl -), @args or die "open pipe: $!";
print $fh $program or die "write to pipe: $!";
close $fh or $! == 0 or warn "close pipe: $!";
__END__
See perldoc -f open and perldoc perlrun.
Of course, there's always eval() too, but that has certain
drawbacks (in particular it executes within the scope and context
of your program and can therefore tamper with it).
#!/usr/bin/perl
use strict;
use warnings;
hello(); # Prints "Hello, World\n!"
my $program = <<'EOF';
use strict;
use warnings;
hello(); # Prints "Hello, Satan!\n"
sub hello {
print "Hello, Satan!\n";
}
EOF
eval $program;
die $@ if $@;
hello(); # Oops, prints "Hello, Satan!\n"
sub hello {
print "Hello, World!\n";
}
__END__
Here is an evil example where the evaled program tampered with
the outer program in ways that may be undesirable. If you control
the inner program then you can do things to make sure that
doesn't happen accidentally (and avoid doing it intentionally).
Thanks to the warnings pragma we do get a warning about it, but
that can be surpressed, and regardless the damage may be done
already.
See perldoc -f eval and perldoc warnings.
Regards,
--
Brandon McCaig <bamcc...@gmail.com> <bamcc...@castopulence.org>
Castopulence Software <https://www.castopulence.org/>
Blog <http://www.bamccaig.com/>
perl -E '$_=q{V zrna gur orfg jvgu jung V fnl. }.
q{Vg qbrfa'\''g nyjnlf fbhaq gung jnl.};
tr/A-Ma-mN-Zn-z/N-Zn-zA-Ma-m/;say'
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