But getting the *number of matches* via that method will depend on the pattern itself --- in list context, the list of matches are returned, but if there are capturing parens the list of captured items are returned (which can be more than 1 per match):

my $text = "my dog is green";
my $count =()= $text =~ /(g)(.)/g;
print $count;
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That prints 4, although the pattern only matched twice. To get the number of matches you'll really need to count them:

my $text = "my dog is green";
my $count;
$count++ while $text =~ /(g)(.)/g;
print $count;
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Or perhaps use the s/// operator (which returns the number of substitutions) and replace everything matched by itself if you don't want to change the string:

my $text = "my dog is green";
my $count = $text =~ s/(g)(.)/$1$2/g;
print $count;
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