how to match an alphanumeric string like the following.

i have to do like the following.

if the input line is

the data is {clock_91b}

i have to replace that with

the string was ("clock_91b")

i tried like

$line =~ s/the data is\s+\{([a-z]+)\}/the string was \(\"$1\"\)/

which is not working.
Is there any idea?