comment on

If I understand correctly your question and desired output one possible way is:

#!/usr/bin/perl
use strict;
use warnings;
use feature 'say';

sub groupWithEachString {
    my %hash;
    $hash{$_}++ for (split //, shift);
    my $str;
    foreach my $character (sort keys %hash) {
    $str .= $character x $hash{$character};
    }
    return $str;
}

my $str = "aaabbbabc";
say groupWithEachString($str);

__END__

$ perl test.pl
aaaabbbbc
[download]

Regarding your second question on how to repeat the process for multiple strings (simply concatenate the strings):

#!/usr/bin/perl
use strict;
use warnings;
use feature 'say';

sub groupWithEachString {
    my %hash;
    $hash{$_}++ for (split //, shift);
    my $str;
    foreach my $character (sort keys %hash) {
    $str .= $character x $hash{$character};
    }
    return $str;
}

my @strings = qw(aaabbbabc aaabbbabc);
my $concatString;
foreach my $string (@strings) {
    $concatString .= $string;
}

say groupWithEachString($concatString);

__END__

$ perl test.pl
aaaaaaaabbbbbbbbcc
[download]

Update: Last part (replace character in a string):

#!/usr/bin/perl
use strict;
use warnings;
use feature 'say';

sub groupWithEachString {
    my %hash;
    $hash{$_}++ for (split //, shift);
    my $str;
    foreach my $character (sort keys %hash) {
    $str .= $character x $hash{$character};
    }
    return $str;
}

my @strings = qw(aaabbbabc aaabbbabc);
my $concatString;
foreach my $string (@strings) {
    $concatString .= $string;
}

my $final = groupWithEachString($concatString);
say $final;

# Replace character in string
$final =~ tr/a/z/;
say $final;

__END__

$ perl test.pl
aaaaaaaabbbbbbbbcc
zzzzzzzzbbbbbbbbcc
[download]

Hope this helps, Thanos.

Seeking for Perl wisdom...on the process of learning...not there...yet!

In reply to Re: Problems with strings by thanos1983
in thread Problems with strings by baxy77bax

Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!

Titles consisting of a single word are discouraged, and in most cases are disallowed outright.

Read Where should I post X? if you're not absolutely sure you're posting in the right place.

Please read these before you post! —

Posts may use any of the Perl Monks Approved HTML tags:

a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr

You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)

	For:		Use:
	&		`&`
	<		`<`
	>		`>`
	[		`[`
	]		`]`

Link using PerlMonks shortcuts! What shortcuts can I use for linking?

See Writeup Formatting Tips and other pages linked from there for more info.