Wildcard expression can be used to select variables with variable names matching the wildcard pattern specified, in workspace nodes. 

For example, the input variable selection for the 2D histogram node in workspace. 

There are some rules/requirements in the wildcard pattern expression.

The rules are pretty simple.  

1. * matches any number of characters.
2. ? matches any single character.
3. For backward compatibility, certain patterns will need to be double quoted in order to be treated as a pattern. Patterns containing spaces or other special characters must be double quoted.

For example:  

• "*[" will match anything that ends with a character [
• "*[*" will match anything that contains character [
• "*[*]" will match anything that contains character [ and ends with a character ]
• "*[?]" will match anything that contains character [ and ends with a character ], and there is only one character between [ and ]
• "* a*" will match anything that contains character a and with space before a 
• * will match everything (need not to be double quoted)
• a* will match anything that starts with the character a (need not to be double quoted)
• *b will match anything that ends with character b (need not to be double quoted)