Aliasing elements
When iterating over a list the iteration variable is aliased to the elements in the list. Thus, it's possible to change the values within the list in a foreach statement:
#!/usr/bin/perl
use warnings;
use strict;
my $g = 99;
foreach my $g (1..5) {
p($g);
}
sub p {
my $l = shift;
printf ("%2d %2d\n", $g, $l);
}
# Output:
#
# 99 1
# 99 2
# 99 3
# 99 4
# 99 5
Localizing variable
The value of the variable in the foreach loop is only visible in the loop (and lost afterwards).
#!/usr/bin/perl
use warnings;
use strict;
my $g = 99;
foreach my $g (1..5) {
p($g);
}
sub p {
my $l = shift;
printf ("%2d %2d\n", $g, $l);
}
# Output:
#
# 99 1
# 99 2
# 99 3
# 99 4
# 99 5