Re: How do I use a block as an ‘or’ clause instead of a simple die?

To process exceptions rather than automatically dying:

eval {
   # my code here
   # for example, a call to whatever subroutine is calling
   # $ftp->put($my_file) or die

   return 1;
} or do {
   my $err=$@;
   # my exception handling code here, uses $err, not $@
}
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And some explanatory notes:

eval {...} is an eval block. It prevents exceptions from killing your script.
return 1; or do {...} will be triggered if (a) something within eval {...} dies or (b) nothing dies, but the final statement evaluates to any "false" value: 0, undef, or the empty string. Since we only want to get into the or do {...} when something dies, we have to make sure that the last line is always true. Returning 1 does that. Note: returning within an eval block only exits the eval block, not any containing sub.
do {....} Anything more than a single statement after "or" needs to be enclosed in a do block.
my $err=$@ $@ holds the exception describing why we died. However, it is rather volatile and gets reassigned the next time we do something wrong. So we save it to another variable before we do anything that could change its value.

Best, beth

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Re^2: How do I use a block as an Ā‘orĀ’ clause instead of a simple die? by CountZero (Bishop) on Apr 18, 2009 at 18:32 UTC
we have to make sure that the last line is always true. Returning 1 does that ~~Your idiom would jump out of any subroutine you are in at the moment. Just `1;` would be sufficient to have a value of 1 'returned' and avoid the `or` branch.~~ Forget the above, it is wrong. As per the docs: `return EXPR`: Returns from a subroutine, eval, or `do FILE` with the value given in EXPR CountZero A program should be light and agile, its subroutines connected like a string of pearls. The spirit and intent of the program should be retained throughout. There should be neither too little or too much, neither needless loops nor useless variables, neither lack of structure nor overwhelming rigidity." - The Tao of Programming, 4.1 - Geoffrey James	[reply] [d/l] [select]

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Re^2: How do I use a block as an Ā‘orĀ’ clause instead of a simple die?
by CountZero (Bishop) on Apr 18, 2009 at 18:32 UTC

we have to make sure that the last line is always true. Returning 1 does that

~~Your idiom would jump out of any subroutine you are in at the moment. Just 1; would be sufficient to have a value of 1 'returned' and avoid the or branch.~~

Forget the above, it is wrong. As per the docs: return EXPR: Returns from a subroutine, eval, or do FILE with the value given in EXPR

CountZero

A program should be light and agile, its subroutines connected like a string of pearls. The spirit and intent of the program should be retained throughout. There should be neither too little or too much, neither needless loops nor useless variables, neither lack of structure nor overwhelming rigidity." - The Tao of Programming, 4.1 - Geoffrey James

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