Another option is to local $/ = \1_048_576; to read the first 1MB:

use strict;
use warnings;
use Digest::MD5 qw/md5_hex/;

my $md5_hex_1m = file_md5_hex_1m('File.txt');
print $md5_hex_1m;

sub file_md5_hex_1m {
    my ( $file, $contents ) = @_;
    local $/ = \1_048_576;

    open my $fh, '<', $file or die $!;
    return Digest::MD5->new()->add($contents)->hexdigest
      if defined( $contents = <$fh> );
}

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In reply to Re: Hash only portion of a file by Kenosis
in thread Hash only portion of a file by myforwik

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