If you must validate user input, it is worth using a prompt module. It not only detects the errors, it gives the user a chance to correct them.

#!/usr/bin/perl
use strict;
use warnings;
use IO::Prompt::Hooked;

my $days = prompt(
    message  =>  "Enter no of days older (1-90):",
    error    =>  "Invalid input, please try again\n",
    validate =>  sub {
        my $days = shift;
        return ( $days =~ /^[1-9]\d?$/  and  $days <= 90 ); 
    },
);

print "You entered $days days\n\n";
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The following sample run shows the recovery from several errors.

:tt.pl
Enter no of days older (1-90):  a
Invalid input, please try again
Enter no of days older (1-90):  !
Invalid input, please try again
Enter no of days older (1-90):  333
Invalid input, please try again
Enter no of days older (1-90):  99
Invalid input, please try again
Enter no of days older (1-90):  07
Invalid input, please try again
Enter no of days older (1-90):  9
You entered 9 days

:
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