The below code is developed based on your logic and I am getting the following output. But I am not getting your expected output. Check whether your expected output is correct.

use strict;
use warnings;

my %p = (A => 2.74, B => 2.64, C => 2.5);
my @range = (50,55,60,65,70,75,80,85,90);

while(my $str = <DATA>){
    chomp($str);
    print "\nInput     : $str\n";
    
    $str =~ s/(\d+)(\w)/($2 . '*') x $1/eg;
    $str =~ s/(\w)(\w)/$1 . '*' . $2 . '*' /eg;    
    $str =~ s/(?!\*)$/*/;    
    $str =~ s/(.)\*(?!\1)/"$1\*\(".$range[ord($1) - 65]."\/100\)\*"/eg
+;
    $str =~ s/\*+$//;    
    
    $str =~ s/$_/$p{$_}/g for (keys %p);
    
    print "Expression: ".$str ."\n";
    print "Output    : ",eval$str ,"\n\n";

}
__DATA__
4ABC
2A2B2C
3C
ABC

Output is:

Input     : 4ABC
Expression: 2.74*2.74*2.74*2.74*(50/100)*2.64*(55/100)*2.5*(60/100)
Output    : 61.38045890064


Input     : 2A2B2C
Expression: 2.74*2.74*(50/100)*2.64*2.64*(55/100)*2.5*2.5*(60/100)
Output    : 53.96012424


Input     : 3C
Expression: 2.5*2.5*2.5*(60/100)
Output    : 9.375


Input     : ABC
Expression: 2.74*(50/100)*2.64*(55/100)*2.5*(60/100)
Output    : 2.98386
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