#!/usr/bin/perl
use strict;
use warnings;

# which file is to be checked
my $file = shift @ARGV;
die "no input file!\n" unless defined $file;

# check with which regex
my $regex = qr/error.*error/;

# open file for reading
open my $fh, '<', $file or die "$file: $!\n";

# try to match regex in file's content
if ( ! grep { m/$regex/ } <$fh> ) {

    # nothing matched; rewind to file's beginning
    seek $fh, 0, 0 or die "can't reposition on filehandle!\n";

    # process file linewise
    while ( my $line = <$fh> ) {
        # process file as desired
        print $line;
    }

    close $fh;
}
# regex matched; don't process file
else {
    close $fh;
    die "error matched!\n";
}

__END__
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