How can I use __DATA__ twice?

perl filehandle
sid_com picture sid_com · Dec 16, 2010 · Viewed 8.7k times · Source

How can I use __DATA__ twice?

#!/usr/local/bin/perl
use warnings;
use 5.012;

while ( <DATA> ) {
    print;
}

while ( <DATA> ) {
    chomp if $. == 1;
    print scalar reverse;
    print "\n" if eof;
}

__DATA__
one
two
three
four
five
six

Answer

Eugene Yarmash picture Eugene Yarmash · Dec 16, 2010

To use the DATA filehandle twice you need to rewind it. The tricky bit is that if you do seek(DATA, 0, 0), it'll be positioned to the first source line, not the line after __DATA__. Therefore you need to save the position first:

my $data_start = tell DATA; # save the position
print while (<DATA>);
seek DATA, $data_start, 0;  # reposition the filehandle right past __DATA__
print while (<DATA>);

See also:

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