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In the code example, I pass a hash by value to a sub, push_1, and push one onto the array,
@{ $hash{$key} }
But when I examine the hash after the sub call, the changes are in the hash, but why is this happening. I thought the hash should have the pre function call values.
#!/usr/bin/perl use strict; use warnings; use Data::Dumper; my %hash; @hash{ 'a'..'d' } = ([175, 450], [0, 350], [0, 50], [300, 50]); print "Initial hash\n"; print Dumper \%hash; print "\nhash after call\n"; push_1(%hash); print Dumper \%hash; sub push_1 { my %hash = @_; for (keys %hash) { push @{ $hash{$_} }, 1; } } __END__ *** Output C:\perlp>perl t.pl Initial hash $VAR1 = { 'c' => [ 0, 50 ], 'a' => [ 175, 450 ], 'b' => [ 0, 350 ], 'd' => [ 300, 50 ] }; hash after call $VAR1 = { 'c' => [ 0, 50, 1 ], 'a' => [ 175, 450, 1 ], 'b' => [ 0, 350, 1 ], 'd' => [ 300, 50, 1 ] }; C:\perlp>

In reply to Pass by value acts like pass by reference by Anonymous Monk

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