$> more file #!/usr/bin/perl -w use strict; _1: f(); _2: d(); _3: f(); sub f { print "F\n"; } sub d { print "D\n"; f(); } $>perl -d:Trace file >> file:4: _1: f(); >> file:8: sub f { print "F\n"; } F >> file:5: _2: d(); >> file:9: sub d { print "D\n"; f(); } D >> file:9: sub d { print "D\n"; f(); } >> file:8: sub f { print "F\n"; } F >> file:6: _3: f(); >> file:8: sub f { print "F\n"; } F