while (<'FILE'>) 
{ $gline = <'FILE'>; 
  print $gline; 
}
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Line 1. while(<'FILE'>)

The <> operator takes a chunk of input from a filehandle, and assigns it to a variable. In this case, to $_, our favorite line noise default variable. So you have said, 'While you can pull a hunk of data out of FILE and stick it into $_, do some stuff.'

Line 2. { $gline = <'FILE'>;

Again with <>. This time you're explicitly assigning to $gfile. To translate into english, 'Put the next hunk of data you get from FILE into $gline.'

Line 3.  print $gline;

Simply print the contents of $gline, which in this case is the even lines of your file.
Try this code ;)

while (<FILE>)
{   $gline = <FILE>;
    push @even, $gline;
}
seek FILE, 0,0;
do
{   $gline = <FILE>;
    push @odd, $gline;
} while (<FILE>);
foreach(0..$#odd)
{ print $odd[$_], $even[$_];
}
[download]

TGI says moo