Hey, there...
The attached perl script gives the output
first is equal to 1
first is equal to 1
first is equal to 1
...
when using "Step over" to debug the statements. Running the script works fine and gives the expected output
first is equal to 1
second is equal to 2
third is equal to 3
As a side note, merging the two print statement gives a different error, it outputs the first line twice, then continues without debugging possibilities.
Test script