use warnings;
use strict;
my @bundle1 = qw/ch3 ch4 ch6/;
my %bundle1 = (
   ch3 => 0,
   ch4 => 0,
   ch6 => 0,
);
my $i = 0;
my @charges = qw/ch1 ch2 ch3 ch4 ch5 ch6 ch7 ch8 ch1 ch2 ch3 ch4 ch5 c
+h1 ch2 ch6 ch7 ch4 ch3 ch9 ch2 ch4/;

foreach my $bundle (@bundle1) {
  foreach my $charge (@charges) {
     if ($bundle eq $charge) {
          $i++;
          $bundle1{$bundle} = $i;
          print $bundle1{$bundle};
     }
  }
}
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Now my main goal I am trying to accomplish is if @bundle1 is found in @charges, then remove the corresponding @bundle1 in @charges and replaced with 'chx'.

So input is--> ch1 ch2 ch3 ch4 ch5 ch6 ch7 ch8 ch1 ch2 ch3 ch4 ch5 ch1 ch2 ch6 ch7 ch4 ch3 ch9 ch2 ch4

So output is--> ch1 ch2 ch5 chx ch7 ch8 ch1 ch2 ch5 ch1 ch2 chx ch7 ch4 ch3 ch9 ch2 ch4