Welcome to the Monastery !

Please read Markup in the Monastery and use <code> tags when you post code - otherwise, your post becomes mangled by html interpretation.

Also, read How do I post a question effectively?. You did not indicate what problem you were having, or what result you were expecting.

Use better variable names, like $name, $pay, $hours instead of $channeln.

Do not use the obsolete "switch" module.

Here is what I can make of your code - not sure what calculation you were trying:

use strict;
use warnings;
use diagnostics;
use feature "say";
use feature "switch";
use v5.22.1;


say "What is your name?";
my $channel1 =<STDIN>;
say "How many hours did you work?";
my $channel2 =<STDIN>;
say "What is your pay?";
my $channel3 = <STDIN>;

chomp for ($channel1,$channel2,$channel3);
say $channel1;
say "Check Amount =  ",
     (40*$channel3)+(($channel2-40)*$channel3*2);
[download]

Output:

e$ perl test-channel.pl 
What is your name?
rrr
How many hours did you work?
44
What is your pay?
10
rrr
Check Amount =  480
[download]