CODEWITHSUNDEEP
perl
frankguthrie
frankguthrie

Reputation: 149

Perl concatenate

I'm watching a training video of UDEMY for perl, but the video is not clear and looks like it contains errors.

The training is showing how to concatenate 2 strings with the following example:

#!usr/bin/perl

print $str = "Hi";
print $str .= " there\n";

However when I run the script it the output is: HiHi There

Where is the second Hi coming from? Am I missing something?

Upvotes: 2

Views: 170

Answers (2)

Gilles 'SO- stop being evil'
Gilles 'SO- stop being evil'

Reputation: 107899

If the training really shows this script, ditch it — it's not code that one would normally write.

$str = "Hi" sets the variable $str to the string "Hi". Most of the time, the value of an assignment is not used, the assignment is only performed for its side effect which is to change the value of the variable. However, in Perl, an assignment does have a value, which is the value that is assigned to the variable. The instruction print $str = "Hi" prints the value that is assigned, i.e. this prints the string "Hi".

The second instructions assigns to $str the value that consists of the old value of $str concatenated with " there\n", i.e. $str is set to "Hi there\n". Once again, the value that is assigned is printed, i.e. this prints the string "Hi there\n".

Normally one would not use the value of the assignments:

#!/usr/bin/env perl
my $str = "Hi";
$str .= " there\n";
print $str;

Upvotes: 7

John
John

Reputation: 727

The first statement assigns the value "Hi" to $str, then prints it. The second statements adds the value " there\n" to $str, making the $str equal to "Hi there\n", then prints it. Thus, the output you're getting is correct for what you're telling the interpreter to do.

Upvotes: 8

Related Questions