chomp and replace in all string in array in Perl efficiently

Question

At the moment I am reading lines from a file, chomp them, and replace tabs by spaces, like so:

open( my $xpfh, '<', $xpathfile ) or die "cannot open file $xpathfile";
    chomp( my @xplines = <$xpfh> );
    close $xpfh;

    foreach my $xpline (@xplines) {
        $xpline =~ s/\t/ /g;
...

As you can see, chomping happens outside the foreach loop, but substitution occurs each iteration. How would one bring that action outside the foreach loop, closer to the chomping? I am asking because I would assume that this is faster than each iteration run a regular expression. Either way, it would be syntactically more pleasing to have all structural operations happen in the same block.

Slurping entire file is already enifficient as long as you deal with non-trivial sizes. You might want to read line-by-line and move chomp into that loop too instead. — Oleg V. Volkov
– Oleg V. Volkov, Commented Feb 25, 2016 at 11:34
How do you know that it's inefficient? Have you benchmarked it? — Matt Jacob
– Matt Jacob, Commented Feb 25, 2016 at 14:39
My point is, don't assume it's inefficient until you have reason to believe it is. What you're doing is called premature optimization. — Matt Jacob
– Matt Jacob, Commented Feb 25, 2016 at 16:18

Sobrique · Accepted Answer · 2016-02-25 11:44:25Z

2

I would probably do it without slurping the file into an array, then iterating the array:

while ( <$xpfh> ) {
    chomp;
    s/\t/ /g;
    print;
}

If you do need the array for some other reason though:

s/\t/ /g for @xplines;

answered Feb 25, 2016 at 11:44

Sobrique

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