replace deprecated given/when by if/elsif in eg/debugger.pl #90

Job	Run time
Build on Linux with Perl 5.32	1m 12s
Build on Linux with Perl 5.30	1m 13s
Build on Linux with Perl 5.20	1m 10s
Native on OS ubuntu-latest Perl 5.32	1m 43s
Test on 5.41.5	1m 51s
Native on OS macos-latest Perl 5.32	8s
Test on 5.40	1m 51s
Native on OS windows-latest Perl 5.32	2m 12s
Test on 5.38	1m 55s
Test on 5.36	1m 52s
Test on 5.34	1m 47s
Test on 5.32	1m 53s
Test on 5.30	1m 53s
Test on 5.28	1m 51s
Test on 5.26	1m 41s
	24m 12s

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