Test if a string contains the key of a hash in Perl - regex

Question

I have a string and want to tell if it contains the key of a hash and if it does I would like to print the value of the hash like so:
#!/usr/bin/perl -w
my %h = ( 'key1' => 'v1', 'key2' => 'v2', 'key3' => 'v3' );
my $str = "this is a string containing key1\n";
if ($str contains a key of %h){
print the value of that key; #i.e v1
}
Whats the best way to do this? (Preferably concise enough to contain in an if statement)

Answer 1

#!/bin/perl -w
my %h = ( 'key1' => 'v1', 'key2' => 'v2', 'key3' => 'v3' );
my $str = "this is a string containing key1\n";
while (($key, $value) = each %h) {
if (-1 != index($str, $key)) {
print "$value\n";
}
}

Answer 2

If you have to search through multiple strings but have just the one unchanging hash, it might be faster to compile the hash keys into a regexp upfront, and then apply that regexp to each string.
my %h = ( 'key1' => 'v1', 'key2' => 'v2', 'key3' => 'v3' );
my $hash_keys = qr/${\ join('|', map quotemeta, keys %h) }/;
my #strings = (
"this is a string containing key1\n",
"another string containing key1\n",
"this is a string containing key2\n",
"but this does not\n",
);
foreach my $str (#strings) {
print "$str\n" if $str =~ $hash_keys;
}

Answer 3

In some cases (big hash, keys are words and you don't want them to match sub-words) this could be the right approach:
my %h = ( 'key1' => 'v1', 'key2' => 'v2', 'key3' => 'v3' );
my $str = "this is a string containing key1 and key3 but notkey2, at least not alone\n";
while ($str =~ /(\w+)/g) {
my $v = $h{$1};
print "$v\n" if defined $v;
}