The use of 'sort' to find a max is always overkill, but can be convenient if efficiency is not an issue. In your case, you probably want 'nsort_by' from the module List::SomeUtils instead of the native 'sort'.

You should be more explicit in describing what you mean by 'number'. Your code finds only continuous strings of decimal digits. (Note: This ignores negative signs. e.g. -124 > 123)

An easy way to find the maximum of the numbers on one line is to use the function 'max' from List::Util

>type SSSufe.pl
use strict;
use warnings;
use List::Util qw(max);
use List::SomeUtils qw(nsort_by);

my @lines = <DATA>;
print ((nsort_by { biggest_on_line($_) } @lines)[-1]);


sub biggest_on_line {
    my $line = shift;
    my @nums = $line =~ /(\d+)/g;
    return max @nums;
}
__DATA__
Hello, i'm 18
1 this year is 2019 1
1 2 3 - 4

>perl SSSufe.pl
1 this year is 2019 1
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