A while loop can be used to do something until a certain condition is true. For example.

#!/usr/bin/perl
use strict;
use warnings;

my $integer = 0;

while ($integer < 5) {
  print "$integer is less than 5 \n";
  ++$integer;
}

Or this.

#!/usr/bin/perl
use strict;
use warnings;

my $integer = 0;

do {
  print "$integer is less than 5 \n";
  ++$integer;
} while ($integer < 5);

. . . will produce the following output.

0 is less than 5 
1 is less than 5 
2 is less than 5 
3 is less than 5 
4 is less than 5