Fix exit() inside BEGIN blocks

[fglock]

Summary

• Fix exit() inside BEGIN blocks to exit the program instead of causing a compilation error
• In Perl, calling exit() inside a BEGIN block terminates the program immediately
• Previously, jperl would catch the PerlExitException and convert it to a "BEGIN failed--compilation aborted" error, then continue parsing and fail

Changes

• Modified SpecialBlockParser.runSpecialBlock() to catch PerlExitException separately and re-throw it
• This allows the exception to propagate to Main.main() which converts it to System.exit()

Test Plan

• Verified exit 0 inside BEGIN block now exits cleanly with exit code 0
• Verified plan skip_all in BEGIN blocks (used by Test::More) now works correctly
• Log4perl tests t/056SyncApp2.t and t/066SQLite.t now skip cleanly without errors

Before/After

Before:

$ ./jperl -e 'BEGIN { exit 0; } print "should not print\n"'
exit 0
BEGIN failed--compilation aborted at -e line 1, near ""

After:

$ ./jperl -e 'BEGIN { exit 0; } print "should not print\n"'
(exits cleanly with code 0)

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