open INFILE,  "<" . $filename 
     or die "Couldn't open file " . $filename . " for reading : $!";
open OUTFILE, ">" . $filename 
     or die "Couldn't open file " . $filename . " for writing : $!";
while (<INFILE>){
    print OUTFILE $_;
    last if /$heading_to_print/;
}
while (<INFILE>){
    print OUTFILE $_ unless /$heading_to_print/;
}
close INFILE;
close OUTFILE;

[download]
A little tip is in your error messages for open() and similar you shuld include the output of $!. Also personally I dont like using global filehandles. I prefer to use lexical ones, but this only works on later versions of Perl.

HTH

UPDATE

This will remove any duplicate lines except the first, not just that of a specific line. (Although it might chew up a lot of memory if there are only a few dupes but many lines.) 

open INFILE,  "<" . $filename 
     or die "Couldn't open file " . $filename . " for reading : $!";
open OUTFILE, ">" . $filename 
     or die "Couldn't open file " . $filename . " for writing : $!";
my %hash;
while (<INFILE>){
    print OUTFILE $_ unless $hash{$_}++;
}
close INFILE;
close OUTFILE;

[download]
This could also be done as a one liner, 
perl -ni.old -e "print $_ unless $_{$_}++" foo.txt

[download]
Which really is quite nice isnt it. :-) (Note that the file will be "edited-in-place", and the original will be backed up as "foo.txt.old")

Yves / DeMerphq
---
Writing a good benchmark isnt as easy as it might look.

In reply to Re: Replacing all but one duplicate lines by demerphq
in thread Replacing all but one duplicate lines by johnirl

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