The code at bottom works fine for converting all alpha characters in a text file to upper (or lower) case.   But having the two "$munged = " lines inside the "for(@in)" loop looks like ineficient if handling large files.

I tried these two tweaks to move that logic outside the for(@in) loop.   The first doesn't work because (correct me if I'm wrong) $_ is empty when $munged is declared.   The second fails with this compilation error: syntax error at uclc.pl line (push @munged, $munged();), near "$munged(" and I'm not clear just what's happening there.

# tweak one
my @munged;
my $munged = lc() if ($uclc eq 'lc');
$munged    = uc() if ($uclc eq 'uc');
for(@in) {
   push @munged, $munged;
   }

# tweak two
my @munged;
my $munged = lc if ($uclc eq 'lc');
$munged    = uc if ($uclc eq 'uc');
for(@in) {
   push @munged, $munged();
   }
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So my questions for the wise bretheren and sisteren are:

1. should I be concerned about potential ineficiency of this code for large input files?
2. if so, how might it be improved?

    cheers,
    Don
    striving toward Perl Adept
    (it's pronounced "why-bick")

#!/usr/bin/perl -w

use strict;

my $uclc    = shift or Usage();
my $infile  = shift or Usage();
my $outfile = shift or Usage();
Usage() unless ($uclc eq 'lc' or 'uc');

open (IN, "< $infile") or die "Error opening $infile for read: $!";
my @in = <IN>;
close IN               or die "Error closing $infile after read: $!";

my @munged;
for(@in) {
   my $munged = lc() if ($uclc eq 'lc');
   $munged    = uc() if ($uclc eq 'uc');
   push @munged, $munged;
   }

open (OUT, "> $outfile") or die "Error opening $outfile for write: $!"
+;
print OUT for(@munged);
close OUT                or die "Error closing $outfile after write: $
+!";

######################################################################
+####
sub Usage {
   die "\n Usage: uclc.pl (lc|uc) infile outfile\n";
   }
######################################################################
+####
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