>perl tkprogressbar.pl

val PBar1: -21.5
val PBar2: -30
("ex1", { as => "temp", val => -30 })
val Labels: -30
("ex1", { as => "temp", val => -30 })

>perl tkprogressbar.pl

val PBar1: -21.5
Use of uninitialized value in concatenation (.) or string at tkprogressbar.pl line 39.
val PBar2:
("ex1", { as => "temp", val => undef })
Use of uninitialized value in concatenation (.) or string at tkprogressbar.pl line 21.
val Labels:
("ex1", { as => "temp", val => undef })