system 'some_command' && die 'cannot execute some_command';

This will always die because it's interpreted as:

system( 'some_command' && die 'cannot execute some_command' );
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Since the string 'some_command' is a true value, the die always executes. To fix this, use and, which has a lower precedence:

system 'some_command' and die 'cannot execute some_command';
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