while (<>) {
    s/^g//;
}
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• Show a few lines of your input (in "code" tags), if you need more help.
• perlintro

Since 500k+ is a big number and the spec says "They all start out with a g", I would rather use substr since there is no need for a test.

while (<>) {
    my $word = substr($_,1); # Start with the second letter
}
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As a note for the OP, while is a nicer option than Foreach Loops in this scenario since, in general, foreach constructs the entire list before incrementing over it, whereas while will just hit your file-handle once per loop -- normally, that means while has a much smaller memory footprint than foreach does for large sets. I don't recall if in the particular case of foreach(<$fh>) { there is an optimization in perl to avoid this pitfall.

---

#11929 First ask yourself `How would I do this without a computer?' Then have the computer do it the same way.

Do we ever have perfect data? I prefer to use a test to warn about invalid data. The following code (untested) makes use of runtime switches (ref: perldoc perlrun). Use -p for the I/O and -i for backup.

#!perl -p -ibak
if (!s/^g(Ord_\d{4}\.png)\s*$/$1/) {
    warn "Invalid line: $_\n";
    $_ = <>;
    redo;
}
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Bill

You can do this on the command line with in-place editing.

johngg@shiraz:~/perl/Monks > cat > gtype.txt
goat
grate
grip
johngg@shiraz:~/perl/Monks > ls gtype*
gtype.txt
johngg@shiraz:~/perl/Monks > perl -pi.BAK -e 's{^g}{};' gtype.txt 
johngg@shiraz:~/perl/Monks > ls gtype*
gtype.txt  gtype.txt.BAK
johngg@shiraz:~/perl/Monks > cat gtype.txt
oat
rate
rip
johngg@shiraz:~/perl/Monks > cat gtype.txt.BAK 
goat
grate
grip
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I hope this is helpful.

Update: See "Command Switches" in perlrun for explanations of -e, -i and -p.

Please show some code and data to help us understand.

see How do I post a question effectively?

#!/usr/bin/perl

use strict;
use warnings;


main(@ARGV);

sub main
{
    
    open(FH, "gtype.txt");
    foreach( my $line = <FH> ) {
        s/^g//; #toolic's idea.
}

}

    close FH;

#and kennethk's idea

#!/usr/bin/perl

use strict;
use warnings;

main(@ARGV);

sub main
{
    open(FH, "gtype.txt");
    while( my $line = <FH> ){
        substr($_,1); # Start with the second letter
}
}
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So, using kennethk's input, I kind of hacked this up...? I can kind of see how it works...

I looked at the perldocs linked in the replies, and I'm still working through them trying to understand all the various differences.

the file I'm working with looks something like this:

gOrd_3342.png

gOrd_3343.png

500k of those going down a file. I need to leave all 500k of those with "Ord_xxxx.png. I have yet to try either of mentioned options, but my idea here is to figure this out and learn at the same time, and not simply get an answer I can plug in and call it quits. Thanks.

Using my $line = <FH> means $_ never gets set so your next line needs to now be $line=substr($line,1);

while (<>) {

}
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