concatenate and print each array element with a suffix - perl

Question

I have some files in a directory like:
A.txt
B.txt
C.txt
I want to print them with new suffix:
#!/user/bin/perl
my #dir_list_initial = `ls *.txt | sed 's/.txt//g' `;
my $suffix = ".dat";
for (my $i=0; $i<=$#dir_list_initial; $i++){
print $dir_list_initial[$i] . $suffix;
}
I expect to print
A.dat
B.dat
C.dat
but it prints
.datA
.datB
.datC

Answer 1

You might try,
chomp(#dir_list_initial);
and later
print $dir_list_initial[$i] . "$suffix\n";
as every element of #dir_list_initial array has newline at the end of string.
Even better it would be to skip shell altogether, and use only perl,
my #dir_list_initial = map { s|\.txt||; $_ } glob("*.txt");

Answer 2

You're doing half of your program by running ls. Don't shell out when you can use builtin Perl mechanisms to do the same job The glob can do everything you're doing with ls and you don't have to depend upon the ls command (what if this is Windows?).
Also, always use strict; and use warnings; in your program, it can save you a ton of grief by picking up common mistakes.
#! /usr/bin/env perl
#
use strict;
use warnings;
use feature qw(say);
for my $file ( glob "*.txt" ) {
chomp $file;
$file =~ s/\.txt$/.dat/;
say $file;
}
Note I'm using s/.../.../ to substitute one suffix with another. You need to learn regular expressions. Your s/.txt// is not correct. The . can stand for any character, and you don't specify that .txt has to be on the end of the string. If my file was called ftxtback.txt, you'd change the file name to .datback.txt which is not what you want.

Answer 3

there's no need for calling sed here, perl can handle that well:
my #dir_list_initial = `ls *.txt`;
chomp #dir_list_initial;
my $suffix = ".dat";
foreach (#dir_list_inital){
s/\.txt$/$suffix/; # this alters #dir_list_initial
print "$_\n";
}
if you have a perl more recent than 5.14, you also can do this:
use 5.014;
my #dir_list_initial = `ls *.txt`;
chomp #dir_list_initial;
my $suffix = ".dat";
say s/\.txt$/$suffix/r foreach #dir_list_initial; # this doesn't alter the array.
and, as mpapec already has pointed out, it would be better to not involve the shell at all:
say s/\.txt$/.dat/r foreach <*txt>