When playing around with some code in answer to reading a line from file two times I found the following odd behaviour:

use warnings;
use strict;

print "Using Perl $]\n\n";

print "Result using DATA:\n\n";
doRead (*DATA);

print "\nResult using file handle:\n\n";
open my $FH, '<', 'noname.pl';
doRead ($FH);
close $FH;


sub doRead {
    my $FH = shift;
    
    while (! eof $FH) {
        my $lineStart = tell $FH;
        my $line = <$FH>;
        
        chomp $line;
        if ($line =~ /^NEWTABLE/) {
            print "Found at $lineStart: >$line<\n";
            seek $FH, $lineStart, 0;
            $line = <$FH>;
            chomp $line;
            print "Reread as >$line<\n";
        }
    }
}

__DATA__
First line
Second line
NEWTABLE - third line
Fourth line

[download]

Prints:

Using Perl 5.008007

Result using DATA:

Found at 627: >NEWTABLE - third line<
Reread as ><
Found at 628: >NEWTABLE - third line<
Reread as ><
Found at 629: >NEWTABLE - third line<
Reread as >NEWTABLE - third line<

Result using file handle:

Found at 629: >NEWTABLE - third line<
Reread as >NEWTABLE - third line<

[download]

Notice that using a "conventional" file handle works as expected, but performing seek on DATA generates rather strange results! Can anyone account for this behaviour?

This was run on Windows XP using AS Perl 5.8.7

DWIM is Perl's answer to Gödel

In reply to An odd thing happend on the way to answering a SoPW - seek DATA oddity by GrandFather

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