Handling errors on perl

limner has asked for the wisdom of the Perl Monks concerning the following question:

Hi i've a small problem about this instruction:

push @tbl, [ @$_ ] for $table->rows

when i launch the my program, occasionally i receive this message:

Can't call method "rows" on an undefined value at download_and_parse_v3.pl line 81.

So, because i want the program goes on even on this error, i tried this in replace of the above instruction:

push @tbl, [ @$_ ] for $table->rows or warn " ERRORE $hname $chin ";

where $hname and $chin are variables in the program that can help me understood the reason of the error.
At this point i thought that i had the above phrase instead the "Can't call method rows..."
but i alwais receive the same message. Where is my mistake? Thanks

Comment on Handling errors on perl Select or Download Code

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Re: Handling errors on perl by Corion (Patriarch) on Aug 19, 2018 at 12:45 UTC
The error is upwards from the code you showed. `$table` did not receive a value. Maybe you have something like this in your code: `$table = Spreadsheet::ParseExcel->parse( $filename );` [download] ... you should check there that you actually get a value back: `my $parser = Spreadsheet::ParseExcel->new(); my $table = $parser->parse('Book1.xls'); if ( !defined $table ) { die $parser->error(), ".\n"; }` [download] But this is just a wild guess as you haven't shown how you intend to initialize `$table`.	[reply] [d/l] [select]
Re: Handling errors on perl by LanX (Saint) on Aug 19, 2018 at 12:41 UTC
use a block eval: `eval { push @tbl, [ @$_ ] for $table->rows } or warn " ERRORE $hname $chin ";` Cheers Rolf _{(addicted to the Perl Programming Language :) Wikisyntax for the Monastery FootballPerl is like chess, only without the dice}	[reply] [d/l]
Re^2: Handling errors on perl by limner (Novice) on Aug 19, 2018 at 16:28 UTC
Hi thank you for your answer. i was able to do the following, and worked very well: `eval { push @tbl, [ @$_ ] for $table->rows };<br> if ($@) {<br> my $error = $@; <br> warn " Custom error type 1 = no problem ";<br> }` [download] this piece of code is inside a perl that is called from another perl so i use "my $error" cause the problem of global $@ and worked as i wanted. Now the small problem left is the following, the message i receive when the error raise is the following: `Custom error type 1 = no problem at perl_parse_v3.pl line 88.` i simply would like to avoid "at perl_parse_v3.pl line 88." because i not necessary cause i perfecly know that only one cause can raise the error. how can that be done?	[reply] [d/l] [select]
Re^3: Handling errors on perl by LanX (Saint) on Aug 19, 2018 at 16:44 UTC
Put a newline \n at the end of your `warn` text. It's described in the second phrase of the documentation. "If the last element of LIST does not end in a newline, it appends the same file/line number text as die does." Cheers Rolf _{(addicted to the Perl Programming Language :) Wikisyntax for the Monastery FootballPerl is like chess, only without the dice}	[reply]
Re: Handling errors on perl by BillKSmith (Monsignor) on Aug 19, 2018 at 22:34 UTC
You should consider using the module Try::Tiny rather than 'eval', especially if you are familiar with its concept from another language. Bill	[reply]