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up vote 3 down vote favorite

I'm not sure what mistake I'm making, but I just changed ne to != and it worked.

This is a simple program to let the user guess a number until they hit a target number.

#!/usr/bin/perl

my $guess = 1;

do {
    $guess = <STDIN>;
} while ( $guess != 12 ) ; # it doesn't work if i replace != with ne

say "you guessed ", $guess;
share|improve this question
    
Welcome to Stack Overflow. Please take the tour and read [how to ask]. Your first question was well-written and well-received. Now that you have a good answer that obviously helped you, the next step is to mark it as accepted so visitors can later see that it solved the problem. – simbabque Jan 9 at 13:31
up vote 12 down vote

Perl's ne is the string not-equal operator, so $guess and 12 are treated as strings.

A string obtained via <> contains a newline character at the end, so it is not equal to the string '12'.

!= is the numeric not-equal operator, so both operands are treated as numbers. In this case Perl will ignore any trailing non-numeric characters when making the conversion, so the newline is ignored and the string 12<newline> is treated as numeric 12.

Were you to chomp the obtained value before comparison, the ne operator would also work.

share|improve this answer
    
Got it. Thank you for your time in giving good explanation. – Nag Jan 8 at 22:35
2  
Since this involves user input it may be good to mention possible trailing spaces as well. – zdim Jan 9 at 5:20

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