Re^6: write and read the same file not display the output

$1 is initialized via regex captures which use parentheses. For example, in the following:

my $string = 'Frank';
my $name   = 'Frank';

print $1 if $string =~ /^$name$/;
print $1 if $string =~ /^($name)$/;
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The first print statement produces:

Use of uninitialized value $1 in...
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Whereas, the second print shows the value in $1:

Frank
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