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Another classic capability of any decent debugger is the ability to display the value of any variable each time its value changes or at requrest.
The X command displays variables in the current package (which is main if no other package has been specified). If the X command is specified by itself, it lists all the variables in the current package, including the system-defined variables and the variables used by the Perl interpreter itself. You need to filter this list to make it useful. There is a special command | to do just that
To print the value of a particular variable or variables, specify the variable name or set of variables names with the X command:
DB<5> X dircount $dircount = '0'
You must not supply the $ character with the variable name when you use the X command. If you supply the $ character (or the @ or % characters for arrays), the debugger displays nothing.
You can use X to display the values of array variables and associative array variables.
DB<6> X regarray @regarray = ( 0 14 1 'hello' 2 36 ) DB<7> X assocarray %assoc_array = ( 'hi' 1 'there' 2 )
Each command prints the subscripts of the array and their values. Regular arrays are printed in order of subscript; associative arrays are printed in no particular order.
If you have an array variable and a scalar variable with the same name, the X command prints both variables:
DB<8> X var
There is no way to use X to display one variable but not the other.
The V command is identical to the X command except that it prints the values of variables in any package. If you specify just a package name, as in the following, this command displays the values of all variables in the package (including system-defined and internal variables):
DB<9> V mypack
If you specify a package name and one or more variable names, as in the following, the debugger prints the values of the variables (if they are defined in that package):
DB<10> V main dircount $dircount = '0'
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