grepre

#!/usr/bin/perl -w

my $re = $ARGV[0];
die "usage: grepre <perl regexp containing a capture buffer>\n"
  unless defined($re);

$re = eval { qr/$re/ };
die "invalid regexp: $@" if $@;

my $exitcode=1;
while (<STDIN>) {
    while (/$re/g) {
        print "$1\n";
        $exitcode=0;
    }
}

exit $exitcode;