#!/usr/bin/perl -w
use strict;

my @files = glob("*.msg");
foreach my $file(@files) {
    open my $in, '<', $file or die "Open fail on $file: $!\n";
    my @lines = <$in>;

    open my $out, '|-', 'perl script.pl' or die "Piping fail: $!\n";
    print $out @lines;
}